The extended M-Ring in the example has forcing path cells denoted by *. These paths are: (2)r3c7-r9c7=(2)r9c5 and (8)r3c7-r13c9=(8)r7c9-r9c78=(8)r9c5. This proves that r3c7=r9c5 = 28 => r3c7<>1. If these 2 cells=2 or if r9c7=2, then r8c7<>2. If these two cells=8 or if r9c78 & r13c9=8, then r23c8<>8. This M-Ring differs from the examplars in Strmckr's post in that the latter has forcing paths which are only 3 cells long whereas in this example the 8 digit has a path which is 5 cells long (counting grouped cells as one). The fact that the 8 digit has an extended path is why I have called it an extended M-Wing. As long as either or both of these paths have an odd number of cells they will work the same as a normal M-Ring.